The present invention relates to a method of manufacturing a roller bearing cage.
Roller bearings are used to provide rotation between two relatively rotating parts, the roller bearing comprising an outer race for mounting to the outer of the two relatively rotating parts, an inner race for mounting to the inner of the two relatively rotating parts, and a set of rollers between the two races, the rollers being mounted in a cage whereby to space the rollers apart. Such an arrangement is well known.
In heavy duty applications, the cage is normally of a metal, such as brass or bronze, and is manufactured as a generally cylindrical item.
However, to allow for the rollers to be replaced, the inner and outer races and the cage may each be provided in two semi-cylindrical halves which are releasably held together. In this way, one half of the outer race may be removed and the cage rotated to successively remove each half of the cage whereby the rollers may be readily replaced when worn. In the case where the cage is made of metal, during manufacture, the initial metal is machined to a cylindrical structure to form a cage blank. However, in the process of cutting the initial cage blank into two semi-cylindrical halves, some of the metal is removed and when the two semi-cylindrical halves are re-engaged with one another (cut edge to cut edge), they will no longer form a circle.
This is normally dealt with by providing spacers between the two semi-cylindrical halves to the cage of a thickness (parallel to the circumference of the cage) to compensate for the material which has been removed in the cutting process but this means that the two semi-cylindrical halves do not directly abut one another which can introduce a lack of rigidity.
The spacer may typically form part of a clip which holds the two semi-cylindrical halves together after they have been reassembled.
As an alternative, the two semi-cylindrical halves may be re-assembled after they have been cut and clipped together without any spacers, so that the reassembled cage is not perfectly cylindrical, and the reassembled cage is re-machined to cylindrical shape. In this case, pockets to mount the rollers are machined in the reassembled cage. This method however adds an extra stage in the manufacturing process.
The present invention reduces or eliminates the necessity for this extra step and the use of spacers.
Through this specification we refer to “semi-cylindrical” halves. Generally the two halves will be produced by a straight cut from side to side of the cage blank through its axis but in some circumstances there may be two cuts may which are not in a line through the cage axis so one semi-cylindrical half may be longer arcuately than the other.